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Summary of Stock Option (Detail)
 3 Months Ended
Mar. 31, 2019
USD ($)
$ / shares
shares
Options  
Beginning balance | shares 1,548,825
Exercises | shares (25,000)
Cancellations | shares (4,500)
Expirations | shares (31,000)
Ending balance | shares 1,488,325
Options exercisable at End of Period | shares 1,273,686
Weighted-average exercise price  
Beginning balance | $ / shares $ 13.87
Exercises | $ / shares 2.19
Cancellations | $ / shares 13.05
Expirations | $ / shares 16.53
Ending balance | $ / shares 14.01
Options exercisable at End of Period | $ / shares $ 13.91
Weighted-average remaining contractual life (years)  
Options outstanding, Ending balance 3 years 9 months 18 days
Options exercisable, Ending balance 3 years
Aggregate intrinsic value  
Options outstanding, end of period | $ $ 219,700
Options exercisable, end of period | $ $ 219,700